The present invention, in some embodiments thereof, relates to a mobile ad-hoc network with dual-type backbone nodes, and, more particularly, but not exclusively, to a mobile ad-hoc network with backbone nodes having satellite communication capabilities.
A mobile wireless/radio ad-hoc network (also denoted herein a MANET) is a self-configuring network of wireless mobile devices without a fixed infrastructure. The wireless devices forming the network (denoted nodes) communicate between each other directly or via other nodes (i.e., a node performs the operation of a router). Nodes may leave or join the network. Since nodes may be mobile, the topology of the network frequently changes. The group of nodes with which a given node is in direct (one-hop) communication changes frequently. Consequently, routes for transmitting messages between nodes must be updated dynamically to ensure efficient and reliable data transmission between nodes. Other constraints (such as hills, buildings, weather etc.) may affect the node's effective range.
Typically each node in a MANET has a unique identification associated therewith. This unique identification enables each node in the network to send a message to another node in the network.
MANET efficiency and performance typically decreases as a function of number of nodes and hops, as well as with throughput increase. Multicast transmissions going through multiple nodes and hops further decrease MANET efficiency. This can lead to bottlenecks and traffic congestion. Mobility and terrain make it hard to predict network congestion bottlenecks.
Many protocols for MANET data routing have been proposed and evaluated based on measures such as the packet drop rate, the overhead introduced by the routing protocol, end-to-end packet delays, network throughput etc.
For purposes of better understanding some embodiments of the present invention, as illustrated in FIGS. 3A-13 of the drawings, reference is first made to the construction and operation of a MANET as illustrated in FIGS. 1 and 2.
FIG. 1 is a simplified diagram of an unclustered mobile ad-hoc network 100. MANET 100 includes nodes (e.g. nodes 110.1-110.4), where each node has a maximal transmit range (as illustrated by dashed circle around node 110.1). The node's transmit range typically varies over time due to the node's mobility and other factors. A line between two nodes (such as between 110.1 and 110.2) indicates that the nodes communicate directly with each other (one-hop). For example, nodes 110.1 and 110.2 are one-hop neighbors. Node 110.3 is a two-hop neighbor of node 110.1, with data being forwarded by node 110.2 (which is a one-hop neighbor of both). It can be seen that data transmission between multi-hop nodes may become complex.
FIG. 2 is a simplified diagram of a clustered mobile ad-hoc network 200. In MANET 200 nodes are dynamically divided into clusters (e.g. the nodes included in 220.1), each cluster having a respective node which has temporarily assumed the role of a super-node (e.g. 230.1), acting as a temporary cluster head for the other neighboring nodes in addition to other node functions. The super-nodes communicate with each other over a separate backbone network (formed from backbone links between super-nodes). Nodes within a given cluster communicate as discussed for FIG. 1. Nodes in separate clusters communicate via the backbone nodes, thus reducing the number of hops required for data transfer between remote nodes and the overall overhead on the MANET. As MANET nodes are mobile and may change location, the status of a node as an ordinary node or as a super-node may change dynamically, in accordance with current network topology, which is affected amongst other factors by the location of all the MANET nodes as well as the terrain topography. As the node operating modes change (e.g. ordinary node becomes super-node and vice-versa), so changes the topology of the backbone link (e.g. backbone link becomes an ordinary link and vice-versa).
International Patent Application Publication No. WO2007122620 by Temelman et al. presents a wireless ad hoc network comprising a plurality of nodes, where each of the nodes has a dynamically determined role. A portion of the nodes are designated with the role of super-nodes and form the routing backbone of the network. Each of the nodes attempts to communicate with at least a minimal number of one hop super-node neighbors. Temelman's network, however, is limited in its capability to provide a geographically wide-spread network in an area having interfering topography.
Additional background art includes:
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